A novel Povarov-type reaction for straightforward synthesis of novel spiro bi-tetrahydroquinolines with readily available 1,2-DHQs (1,2-dihydroquinolines) and aromatic imines was developed. The reaction could be selectively stopped at the first stage under a Brønsted acid catalyst to afford the corresponding functionalized 1,2-DHQs conveniently.

The mimics of vitamin B6-dependent enzymes that catalyzed an enantioselective full transamination in the pure aqueous phase have been realized for the first time through the establishment of a new “pyridoxal 5′-phosphate (PLP) catalyzed non-covalent cyclodextrin (CD)-keto acid inclusion complexes” system, and various optically active amino acids have been obtained.

A three component reaction with two different ketones and aromatic amines was firstly investigated. The difference in reactivity between ordinary ketones and ketone esters allowed for the production of 1,2-DHQs efficiently. The possible Skraup reaction with 2 equiv. of the same ketones was prohibited due to the fast formation of imines.

•The method provided a concise methodology for the synthesis of chiral indolines.•An external hydride transfer agent was used for the KR of racemic indolines.•The reaction was good complementary to Akiyama’s work.We have developed a highly efficient and practical strategy for the kinetic resolution of indoline derivatives, involving a chiral Brønsted acid-catalyzed iminium ion formation and asymmetric transfer hydrogenation cascade process. The kinetic resolution allows the synthesis of 2-substituted N-benzylindolines in good yields with moderate to excellent enantioselectivities.Download high-res image (75KB)Download full-size image

AbstractA variety of C3-, C6-, C8- and C13-functionalized 1,2-dihidroquinolines (1,2-DHQs) have been prepared through post-modification of simple 1,2-DHQs by regioselective Friedel–Crafts alkylations. Several commonly used electrophiles such as 3-indolylmethanol derivatives, nitroolefins, 1,4-benzoquinones, aromatic aldehydes and ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline were rationally used to afford the corresponding 1,2-DHQs with high yield and regioselectivity. The regioselectivity of the reaction appears to be governed by the substituents of the 1,2-DHQ substrates.

A new guideline for the construction of hammerhead ribozymes to achieve trans-cleavage of a single-stranded RNA molecule was developed. The sequence rule of the HHRz cleavage site was highly recommended to be “DWH” with an optimal binding arm length of 8–9nt, which diverged from the former rule of “NUX”.

In situ generation of the reactive amphoteric α-amino aldehyde with simple α-hydroxy ketones and phenylamine via Heyns rearrangement was proven to be feasible. Metal-free domino reactions based on this reactive intermediate were effectively used to afford important N-heterocycles including polysubstituted pyrroles, indoles, and quinoxalines conveniently. A simple starting material, water as the only byproduct, and diversity of the useful products will make this method greatly attractive for pharmaceutics.

Tetrahydroquinolines (THQs) with an all-carbon quaternary stereocenter were effectively obtained via the in situ formation of aza-ortho-xylylene (AOX) with easily accessible 1,2-dihydroquinolines as precursors. The reaction was rationalized with chiral phosporic acid to afford chiral THQs with high yield and excellent enantioselectivity.

Polymerase chain reaction coupled with signal generation offers sensitive recognition of target DNA sequence; however, these procedures require fluorophore-labeled oligonucleotide probes and high-tech equipment to achieve high specificity. Therefore, intensive research has been conducted to develop reliable, convenient, and economical DNA detection methods. The relay PCR described here is the first sequence-specific detection method using a small-molecule fluorophore as a sensor and combines the classic 5′–3′ exonuclease activity of Taq polymerase with an RNA mimic of GFP to build a label-free DNA detection platform. Primarily, Taq polymerase cleaves the 5′ noncomplementary overhang of the target specific probe during extension of the leading primer to release a relay oligo to initiate tandem PCR of the reporting template, which encodes the sequence of RNA aptamer. Afterward, the PCR product is transcribed to mRNA, which could generate a fluorescent signal in the presence of corresponding fluorophore. In addition to high sensitivity and specificity, the flexibility of choosing different fluorescent reporting signals makes this method versatile in either single or multiple target detection.

We identified a new class of deoxyribozymes named A-2 and A-3 by in vitro selection which required both Cu2+ and Mn2+ as cofactors that selectively and rapidly cleave the DNA substrate. Studies confirmed that they cleaved via a mechanistic pathway involving the formation of hydrogen peroxide as the reactive species. The kinetics, secondary structures and sequence tolerance of the new class of the deoxyribozymes A-2 and A-3 were reported.

•Benzylic C–H bond of pyridines were functionalized with ordinary aromatic imines.•Simple Brønsted acids efficiently catalyzed the reactions.•Poly-substituted pyridines were obtained from accessible aromatic Hantzsch esters.An exceptionally simple and environmentally friendly methodology has been developed for directly functionalizing the benzylic C–H bond of the poly-substituted pyridines with aromatic imines. Simple Brønsted acid catalysts including salicylic acid and TsOH were successfully employed. Different types of poly-substituted pyridines could be efficiently obtained with moderate yields. Traditional ways to such types of pyridines involved the aromatization of the corresponding Hantzsch 1,4-dihydropyridines, while this method greatly simplified the synthetic procedures.An exceptionally simple and environmentally friendly methodology has been developed for the synthesis of poly-substituted pyridines with easily accessible substrates.

A new way of forming the aza-o-xylylene with easily accessible 1,2-dihydroquinolines as precursor has been developed. The presence of an electron-donating group at the proper position of 1,2-dihydroquinoline was crucial for protonation of the alkene through dearomatization with a simple Brønsted acid. The in situ forming reactive intermediate was trapped with Hantzsch ester to afford tetrahydroquinolines in excellent yield and enantioselectivity.

Fluorescence-activated cell sorting (FACS) was exploited to isolate Escherichia coli cells that were highly fluorescent due to the expression of RNA aptamers that induce fluorescence of 3,5-difluoro-4-hydroxybenzylidene imidazolinone. Two different aptamers, named ZT-26 and ZT-324, were identified by this method and compared to the fluorescence-signaling properties of Spinach, a previously reported RNA aptamer. Aptamer ZT-26 exhibits significantly enhanced fluorescence over Spinach only in vitro. However, aptamer ZT-324 is 36 % brighter than Spinach when expressed in E. coli. The FACS-based selection strategy presented here is attractive for deriving fluorescent RNA aptamers that function in cells as it directly selects for cells with a high level of fluorescence due to the expression of the RNA aptamer.

Alkyl substituted Hantzsch esters are rationally used as alkylation reagents to replace the nitro groups of nitro olefins to give excellent yields of trans-olefins. The reaction mechanism is considered to proceed through a free radical mechanism, which is different from the corresponding transfer alkylation of imines.

•We have established an operation-convenient and cost-effective way for detection HBV.•This method has shown good performance with a broad range of linearity and high sensitivity.•The results of detection is reported with macroscopic colorimetric signals.•The strategy takes the key advantage of the TaqMan technology and use inexpensive DNA sensor.•This approach can detect HBV DNA qualitatively or quantificationally.Hepatitis B virus (HBV) can cause viral infection that attacks the liver and it is a major global health problem that put people at a high risk of death from cirrhosis of the liver and liver cancer. HBV has infected one third of the worldwide population, and 350 million people suffer from chronic HBV infection. For these reasons, development of an accurate, sensitive and expedient detection method for diagnosing, monitoring and assessing therapeutic response of HBV is very necessary and urgent for public health and disease control. Here we report a new strategy for detection of viral load quantitation of HBV based on colorimetric polymerase chain reaction (PCR) with DNAzyme-containing probe. The special DNAzyme adopting a G-quadruplex structure exhibited peroxidase-like activity in the presence of hemin to report colorimetric signal. This method has shown a broad range of linearity and high sensitivity. This study builds important foundation to achieve the specific and accurate detection level of HBV DNA with a low-cost and effective method in helping diagnosing, preventing and protecting human health form HBV generally all over the world and especially in developing countries.

•Ribozyme glmS based isothermal amplification for metabolites.•Colorimetric detection of glucosamine-6-phosphate (GlcN6P).•Promising platform for high-throughput screening of glmS riboswitch antibiotics.Ribozyme glmS based isothermal amplification assay is developed for the colorimetric detection of glucosamine-6-phosphate (GlcN6P). Upon binding to the metabolite target GlcN6P, self-cleavage of glmS ribozyme is initiated to release RNA fragment that can trigger the cascade signal amplification to release large amount of G-quadruplex DNAzymes as reporter for colorimetric detection. Given the importance of GlcN6P for cell wall biosynthesis, the glmS riboswitch has become a new drug target for the development of antibiotics. This assay not only offers a convenient detection of GlcN6P with high specificity and sensitivity, but also provides a platform for high-throughput screening of antibiotics based on glmS riboswitches.

RNA/DNA primer pairs and two polymerases were used to efficiently amplify DNA sequences using the conventional polymerase chain reaction (PCR). The reaction required the use of both DNA polymerase and reverse transcriptase during each thermal cycle and formed a double-stranded DNA in which one terminus was an RNA/DNA hybrid. Because there is a higher sensitivity of the DNA polymerase to the mismatch at the 3′-end in the RNA/DNA hybrid duplex than in the DNA/DNA duplex, the RNA-primed PCR reveals much better specificity in the allele-specific PCR to detect single-nucleotide mutation.

We have developed an organocatalytic asymmetric Michael reaction of acylsilane through the selection of acylsilane substrates and organocatalysts, thus creating a rare example of acylsilane α-alkylation with a chiral guanidine catalyst, which afforded products in good yields and high stereoselectivity. The corresponding adducts described here have also been demonstrated to be useful in the synthesis of unnatural amino acids and biologically active compounds.

A novel DNA display strategy, based on a new puromycin modifier, has been developed. The 5′-end puromycin-tethered oligonucleotide was synthesized to hybridize with mRNA, so that it could attack the nascent polypeptides during in vitro translation. The DNA–peptide fusion molecule can tolerate more harsh and stringent selection conditions, therefore, this DNA display may become a useful tool for in vitro display technologies for the selection of peptide drug candidates.

Fast and accurate detection of single-nucleotide polymorphism (SNP) is thought more and more important for understanding of human physiology and elucidating the molecular based diseases. A great deal of effort has been devoted to developing accurate, rapid, and cost-effective technologies for SNP analysis. However most of those methods developed to date incorporate complicated probe labeling and depend on advanced equipment. The DNAzyme based Gap-LCR detection method averts any chemical modification on probes and circumvents those problems by incorporating a short functional DNA sequence into one of LCR primers. Two kinds of exonuclease are utilized in our strategy to digest all the unreacted probes and release the DNAzymes embedded in the LCR product. The DNAzyme applied in our method is a versatile tool to report the result of SNP detection in colorimetric or fluorometric ways for different detection purposes.Highlights► DNAzyme based Gap-LCR detection method averts any chemical modification on probes by incorporating a short functional DNA sequence into one of LCR primers. ► Two kinds of exonuclease are utilized in our strategy to digest all the unreacted probes and release the DNAzymes embedded in the LCR product. ► The DNAzyme applied in our method is a versatile tool to report the result of SNP detection in colorimetric or fluorometric ways for different detection purposes.

A new method of enantioselective synthesis of (S,S)-2,8-diazobicyclo [4.3.0] nonane was found by using (R)-2-amino-2- phenyl-ethanol as chiral induction reagent. The entire synthetic process included 8 steps which were easy to operate with high yield. The purification method was only simple recrystallization or even used directly in the next step without further purification. The total yield was 29%.

A protein-free, isothermal, self-amplified nucleic acid sensing system which was a G-quadruplex integrated hybridization chain reaction (GQ-HCR) system was developed. The G-quadruplex was closed two-thirds in the loop and one-third in the stem of one of the GQ-HCR hairpin probes. In the absence of the target molecule, the GQ-HCR probes stayed as inactive meta-stable hairpin structures and the G-quadruplex was inert. Reversely, the GQ-HCR probes could be cross-opened to start a hybridization chain reaction and the closed G-quadruplex could be released to be free when the GQ-HCR probes came across the target molecule. The GQ-HCR nucleic acid sensing system could detect as low as 7.5 nM ssDNA or RNA by the colorimetric method and 4 nM ssDNA by the fluorometric method. Less than 10 copies of dsDNA template could also be detected when PCR was combined with the GQ-HCR system (PCR+GQ-HCR). Because of these advantages, the GQ-HCR system was also studied for application in visual chip detection to obtain a satisfactory repeatable and specific result.Highlights► Protein-free, isothermal, self-amplified nucleic acid sensing system GQ-HCR via the integration of intact G-Quadruplex and HCR for the colorimetric or fluorimetric detection of single-stranded DNA or RNA. ► In order to detect double stranded DNA and get much better detection sensitivity, we improved the detection system further through the combination of PCR with GQ-HCR. ► GQ-HCR system is an ideal platform to develop visual-chip based nucleic acid detection.

The first successful enantioselective intermolecular bromoesterification was realized by using a chiral phosphoric acid as a catalyst. The reaction was optimized after screening 2-aminopyridine based basic catalysts, cinchona alkaloid based basic catalysts, and binol backbone based Brønsted acid catalysts. Up to 70% ee and a moderate yield were achieved under the optimized condition. An ion-pair mechanism has been suggested in order to explain the reaction results.(1S,2S)-2-Bromocyclohexyl benzoateC13H15BrO2[α]D25=+12.6 (c 0.1, CH2Cl2) ee: 55%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 4-methoxybenzoateC14H17BrO3[α]D25=+2.5 (c 0.07, CH2Cl2) ee 40%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 4-nitrobenzoateC13H14BrNO4[α]D25=+1.6 (c 0.07, CH2Cl2) ee 41%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 4-cyanobenzoateC14H14BrNO2[α]D25=+4.8 (c 0.07, CH2Cl2) ee: 35%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-hydroxybenzoateC13H15BrO3[α]D25=+3.5 (c 0.1, CH2Cl2) ee 34%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-oxo-2-phenylacetateC14H15BrO3[α]D25=+7.1 (c 0.10, CH2Cl2) ee 30%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-(furan-2-yl)-2-oxoacetateC12H13BrO4[α]D25=+2.2 (c 0.10, CH2Cl2) ee: 44%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-oxo-2-(thiophen-2-yl)acetateC12H13BrO3S[α]D25=+7.7 (c 0.1, CH2Cl2) ee 39%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-phenylacetateC14H17BrO3[α]D25=+11 (c 0.15, CH2Cl2) ee 57%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-(2-methoxyphenyl)acetateC15H19BrO3[α]D25=+6.2 (c 0.10, CH2Cl2) ee: 70%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-(3-methoxyphenyl)acetateC15H19BrO3[α]D25=+10.2 (c 0.7, CH2Cl2) ee 67%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-(4-methoxyphenyl)acetateC15H19BrO3[α]D25=+14.2 (c 0.1, CH2Cl2) ee 69%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-(4-fluorophenyl)acetateC14H16BrFO2[α]D25=+10.2 (c 0.20, CH2Cl2) ee: 53%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-(2-nitrophenyl)acetateC14H16BrNO4[α]D25=+2.2 (c 0.07, CH2Cl2) ee 63%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 2-(naphthalen-1-yl)acetateC18H19BrO2[α]D25=+5.0 (c 0.1, CH2Cl2) ee 53%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 1-naphthoateC17H17BrO2[α]D25=+4.8 (c 0.10, CH2Cl2) ee: 28%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclohexyl 3-phenylpropanoateC15H19BrO2[α]D25=+8.5 (c 0.1, CH2Cl2) ee 33%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclopentyl benzoateC12H13BrO2[α]D25=+3.7 (c 0.1, CH2Cl2) ee 20%Source of chirality: the precursorAbsolute configuration: (1S,2S)(1S,2S)-2-Bromocyclooctyl benzoateC17H17BrO2[α]D25=+5.8 (c 0.10, CH2Cl2) ee: 10%Source of chirality: the precursorAbsolute configuration: (1S,2S)(2R,3S)-3-Bromotetrahydro-2H-pyran-2-yl benzoateC12H13BrO3[α]D25=+2.8 (c 0.1, CH2Cl2) ee 7.5%Source of chirality: the precursorAbsolute configuration: (1S,2S)

Alkyl substituted Hantzsch esters are rationally used as alkylation reagents to replace the nitro groups of nitro olefins to give excellent yields of trans-olefins. The reaction mechanism is considered to proceed through a free radical mechanism, which is different from the corresponding transfer alkylation of imines.

We identified a new class of deoxyribozymes named A-2 and A-3 by in vitro selection which required both Cu2+ and Mn2+ as cofactors that selectively and rapidly cleave the DNA substrate. Studies confirmed that they cleaved via a mechanistic pathway involving the formation of hydrogen peroxide as the reactive species. The kinetics, secondary structures and sequence tolerance of the new class of the deoxyribozymes A-2 and A-3 were reported.

Tetrahydroquinolines (THQs) with an all-carbon quaternary stereocenter were effectively obtained via the in situ formation of aza-ortho-xylylene (AOX) with easily accessible 1,2-dihydroquinolines as precursors. The reaction was rationalized with chiral phosporic acid to afford chiral THQs with high yield and excellent enantioselectivity.

A new guideline for the construction of hammerhead ribozymes to achieve trans-cleavage of a single-stranded RNA molecule was developed. The sequence rule of the HHRz cleavage site was highly recommended to be “DWH” with an optimal binding arm length of 8–9nt, which diverged from the former rule of “NUX”.

We have developed an organocatalytic asymmetric Michael reaction of acylsilane through the selection of acylsilane substrates and organocatalysts, thus creating a rare example of acylsilane α-alkylation with a chiral guanidine catalyst, which afforded products in good yields and high stereoselectivity. The corresponding adducts described here have also been demonstrated to be useful in the synthesis of unnatural amino acids and biologically active compounds.